Exploiting Externalities to Estimate the Long-Term Effects of Early Childhood Deworming

Owen Ozier, World Bank Group

I investigate whether a large-scale deworming intervention aimed at primary school pupils in western Kenya had long-term effects on young children in the region, exploiting positive externalities from the program to estimate the impact on younger children who did not receive treatment directly. I find large cognitive effects—equivalent to between 0.5 and 0.8 years of schooling—for children who were less than one year old when their communities received mass deworming treatment. Because mass deworming was administered through schools, I also estimate effects among children who were likely to have older siblings in school to receive the treatment directly; in this sub-population, effects are nearly twice as large.